The present invention relates to a bonded composite of a first thin-section element of sheet material and a second thin-section element bonded together by a bond pattern. More particularly, one of the contemplated applications for the present invention is in bonding outer cover and body side liner thin-section elements of absorbent articles to one another.
Absorbent articles have been known for a long time as personal care hygiene products. Absorbent articles find use, for example, as diapers, training pants, incontinence products, women""s sanitary pads, and the like. Such absorbent articles are designed and constructed to absorb and store liquid bodily excretions such as urine, menstrual fluid, or blood. Women""s sanitary pads are used, for example, to absorb the liquids excreted prior to, during, and after menstruation.
In absorbent articles, the portions of the article where different layers or components are bonded to each other tend to incur significant stress concentrations, and in absorbent articles using conventional bond patterns, tend to fracture at those bonded locations under such stresses. In conventional patterns used in absorbent articles, bond locations are disposed in uniform and crossing straight lines and straight rows of circular bond elements. The inventors herein have noted that such bond configuration has been found to enhance the probability that the absorbent article will tear and that the tear propagates along the side edge of the bond pattern. Tearing properties of such conventional patterns can be compared to perforated paper forms.
The problem addressed in the present invention is thus to provide a bonded composite demonstrating a bond pattern, and an absorbent article implementing the bond pattern, whereby the configuration of the bond pattern discourages the possibility for fracture of the bonded composite or absorbent article at the bond pattern.
The present invention solves this problem by means of the bonded composite as well as the absorbent article both disclosed and described in the independent claims. Additional advantageous embodiments of the absorbent article in accord with the invention and of the process in accordance with the invention arise from the dependent claims, the specification, and the drawings.
It is an object of this invention to reduce the ease of tearing of a bonded composite or absorbent article by introducing bonding patterns which discourage straight fracture of the bonded materials, and encourage dissipating an initially concentrated force within a substantial area of the bonding pattern.
In a first family of embodiments, the invention comprehends a bonded composite. The bonded composite comprises, as a first thin-section element, a first layer of sheet material, a second thin-section element bonded, to the first thin-section element, at least in part by bond elements, and at least in part by adherent material. The adherent material is disposed between the first and second thin-section elements proximate and about ones of the bond elements. The adherent material, at least in part, bonds the thin-section elements to each other at loci of the adherent material. The combination of the adherent material and the bond elements defines a bond pattern.
The bond pattern has a pattern length, a pattern width represented by first and second side edges of the bond pattern, and a central longitudinal axis, typically centered on the bond elements. The side edges of the bond pattern and a corresponding pattern area between such side edges are defined generally by those areas of the respective thin-section elements which participate in absorbing and dissipating, by operation of the bond pattern, stresses received into the bond pattern from external sources.
The bond pattern has a pattern density defined generally by the fraction of the pattern area occupied by the bond elements. The bond elements proximate the side edges are spaced farther apart from each other than bond elements disposed more away from the side edges, thus creating a relatively less dense portion of the bond pattern proximate the side edges of the pattern, as measured by bond element fraction of the pattern area, and a relatively more dense portion of the bond pattern, as measured by bond element fraction of the pattern area, away from the side edges.
The bond pattern reflects application of force urging the first and second thin-section elements toward each other in face-to-face relationship to form an array of separate, distinct, and spaced elongate bond elements affixing the first and second thin-section elements to each other.
Bonds corresponding to the bond elements are activated by combined application of adherent material, pressure, and one of thermal energy or ultrasonic-frequency energy to at least one of the first and second thin-section elements.
In some embodiments, the bond pattern comprises, as ones of the bond elements, a first sub-array of longitudinally-oriented separate, distinct, and spaced stress receptor elements disposed along the length, and proximate the side edges of, the bond pattern. In such embodiments, the bond pattern can also comprise, as ones of the bond elements, a second sub-array of longitudinally-oriented separate, distinct, and spaced transfer and dissipation elements spaced along the length of the bond pattern, typically inwardly of the side edges of the bond pattern and generally inwardly of the stress receptor elements. Respective ones of the transfer and dissipation elements can have first ends disposed toward an interior of the bond pattern. The respective transfer and dissipation elements can extend to second ends adjacent the side edges of the bond pattern between respective ones of the stress receptor elements. The stress transfer and dissipation elements can direct stresses inwardly into the interior of the bond pattern, and can dissipate such stresses on the interior of the bond pattern.
In preferred embodiments, the adherent material comprises adhesive selected from the group consisting of contact adhesives, pressure sensitive adhesives, hot melt adhesives, two-part chemically activated adhesives, and mixtures and blends of such adherent materials.
The adherent material can be distributed and/or dispersed between the first and second thin-section elements as a result of the force being applied to the thin-section elements, such distribution and/or dispersal of the adherent material assisting in defining outer transverse edges of the adherent material in the bond pattern.
In preferred embodiments, at least one of the first thin-section element and the second thin-section element comprises polymeric material selected from the group consisting of polyolefins including polyethylenes and polypropylenes, polyesters, and polyamides, and copolymers, mixtures, and blends of such polymeric materials.
Generally, at least one of the first thin-section element and the second thin-section element comprises a fibrous web defining a multiplicity of randomly-spaced small openings extending from a major surface of the web into the interior of the web.
In some embodiments, the bond elements define the bond pattern in a repeating arrangement of pattern segments.
In some embodiments, outer edges of the adherent material define an adherent material pattern corresponding with at least about 50 percent of the pattern area of the bond pattern, preferably, with at least about 75 percent of the pattern area of the bond pattern, more preferably, with substantially all of the pattern area of the bond pattern.
In a second family of embodiments, the invention comprehends a bond pattern, reflecting application of force, which urges the first and second thin-section elements toward each other in face-to-face relationship to form an array of separate, distinct, and spaced elongate bond elements affixing the first and second thin-section elements to each other. Bonds corresponding to the bond elements are activated by a combined application of adherent material, pressure, and one of thermal energy or ultrasonic-frequency energy to at least one of the first and second thin-section elements. The adherent material is one or both distributed and dispersed between the first and second thin-section elements as a result of the force being applied to the thin-section elements. One or both of the distribution and dispersal of the adherent material assist in defining outer transverse edges of the adherent material in the bond pattern.
As ones of the bond elements, a first sub-array of longitudinally-oriented separate, distinct, and spaced stress receptor elements is disposed along the length, and proximate the side edges of, the bond pattern. A second sub-array of longitudinally-oriented separate, distinct, and spaced transfer and dissipation elements is spaced along the length of the bond pattern, preferably inwardly of the side edges of the bond pattern and preferably generally inwardly of the stress receptor elements. Respective transfer and dissipation elements have first ends disposed toward an interior of the bond pattern, and which extend to second ends adjacent the side edges of the bond pattern between respective ones of the stress receptor elements. The stress transfer and dissipation elements direct stresses inwardly into the interior of the bond pattern, and assist in dissipating such stresses on the interior of the bond pattern.
In a third family of embodiments, the invention comprehends as ones of the bond elements, a first sub-array of longitudinally-oriented separate and distinct stress receptor elements disposed proximate the side edges of the bond pattern, and spaced at first distances from each other along the length of the bond pattern, and a second sub-array of longitudinally-oriented separate and distinct transfer and dissipation elements preferably disposed inwardly of the side edges and preferably inwardly of the stress receptor elements, and at second distances from the stress receptor elements less than the spacing of respective ones of the stress receptor elements from each other.
In some embodiments, respective transfer and dissipation elements have first ends disposed toward an interior portion of the bond pattern, and extending to second ends adjacent the side edges of the bond pattern between respective ones of the stress receptor elements. In such embodiments, the transfer and dissipation elements direct stresses inwardly to the interior portion of the bond pattern, and assist in dissipating such stresses at the interior portion of the bond pattern.
In a fourth family of embodiments, the invention comprehends an absorbent article having a front portion and a rear portion, and a crotch portion extending between the front portion and the rear portion. The absorbent article comprises, as a first thin-section element, a first layer of sheet material, and a second thin-section element bonded to the first thin-section element, at least in part, by bond elements. The absorbent article further comprises adherent material disposed between the first and second thin-section elements proximate and about ones of the bond elements. The adherent material at least in part bonds the thin-section elements to each other at loci of the adherent material, the combination of the adherent material and the bond elements defining a bond pattern. The absorbent article also comprises an absorbent core disposed adjacent at least one of the first thin-section element and the second thin-section element.
In a fifth family of embodiments, the invention comprehends a process for bonding a first thin-section element and a second thin-section element to each other. The process comprises applying an adherent material to at least one of the first and second thin-section elements over at least part of an area of the respective thin-section material which is to be bonded. The process further comprises bringing the first and second thin-section elements together, including at the area to be bonded. Additionally, the process includes applying force urging the first and second thin-section elements toward and into surface-to-surface contact with each other including at the area to be bonded, and applying at least one of thermal energy or ultrasonic-frequency energy to at least one of the first and second thin-section elements in the area to be bonded, thereby forming an array of elongate bond elements and activating the adherent material proximate and generally about ones of the bond elements.